A) Field of the Invention
The present invention relates to a one way clutch mechanism employed in a stator assembly of a torque converter. The invention further relates to a method of manufacturing the stator having the one way clutch mechanism.
B) Description of Related Art
Torque converters are commonly used to transmit torque from an engine to a transmission in an automobile. A typical torque converter generally includes three main components, an impeller, a turbine and a stator all disposed within a torque converter housing. The torque converter housing is usually filled with hydraulic fluid. In such a torque converter, the stator or a wheel stator assembly is functionally disposed between the impeller and the turbine. The wheel stator assembly includes a ring-shaped stator carrier, a plurality of stator blades provided on an outer circumferential surface of the stator carrier, an outer race fixed to the stator carrier at its inner circumferential portion, an inner race placed close to an inner circumferential portion of the outer race and a one-way clutch placed between the inner and outer races. Typically, the stator assembly engages a stator shaft fixed to the transmission so as not to rotate relative to the transmission.
The one-way clutch employed in the clutch includes a plurality of rollers and a plurality of elastic elements for urging the rollers in a first circular direction. The elastic elements are supported by projections provided on an inner circumferential surface of the outer race. The projections are formed integral with the outer race or may be made of separate components. Friction surfaces are formed in the inner circumferential surface of the outer race corresponding to the positions where the rollers are disposed. In combination with the outer circumferential surface of the inner race, the friction surfaces define a plurality of clearance gaps which become greater in radial width toward the first circular directions.
In this one-way clutch, when force is applied to the outer race in the first circular directions, the rollers are urged toward narrower portions of the clearance gaps in their radial widths and are frictionally engaged with the inner race. Hence, the outer race and the stator carrier cannot rotate relative to the inner race, and torque transmission can be performed between them. Under this condition, the elastic elements urge the rollers in the first circular direction. When force is applied to the outer race in a second circular direction to rotate it, the rollers compress the elastic elements and move them toward larger portions of the clearance gaps in their radial widths, so that the rollers can be released from frictional engagement. Consequently, the outer race rotates relative to the inner race, and the torque transmission between them is discontinued.
In the conventional wheel stator assembly as described above, the process of forming the projections integral with the outer race at its inner circumferential portion is a complicated one and can cause an increase in fabrication costs. In a configuration where the projections are formed separate components with the outer race, the separate components must be prepared independently, then rate process, which also leads to an increase in the fabrication cost.